Abstract

Background Tocilizumab (TCZ) is a monoclonal IL6-receptor antibody which is indicated in adult patients either as monotherapy or in combination with methotrexate for treatment of moderate to severe RA.1 Dosing is usually adopted to the patients' weight. An infusion of 1 hour every four weeks is the recommended standard infusion regimen.

Objectives The purpose of this analysis was to investigate the influence of body mass index (BMI) on patient related treatment outcomes in patients with RA treated with TCZ. Furthermore, we investigated whether maintaining the recommended dosage regimen had an effect on outcomes.

Methods 60 patients with at least moderate RA were retrospectively analyzed. Patients were divided into two groups according to the median of the BMI. After treatment with TCZ over a period of 6 months, outcomes were compared between these two groups. Endpoints of our analysis were reduction of the DAS28 score (ESR and CRP), TJC and SJC numbers and concomitant dosage of glucocorticoids (GC). In addition, patients who complied with the infusion regimen were compared to patients who did not.

Results The mean age of the study population was 56 years. 88.3% had been treated with biologicals. >90% were categorized in the moderate disease activity group according to the DAS28 score. The proportion of patients who complied with the recommended dosage regimen was similar in both BMI groups (73.3% for low BMI vs. 86.7% for high BMI, p=0.20). In both groups, treatment with TCZ over 6 months led to a significantly reduced DAS28, TJC and SCJ number as well as a reduced need for GC. The amount of reduction was not statistically different in both groups (DAS28 reduction in low BMI 1.5 (0.9-3.0) vs. 2.3 (1.6-3.8) in high BMI, p=0.09, TJC reduction 4 (2-7) vs 6 (2-13), p=0.17, SJC reduction 2 (1-5) vs 4 (0-10), p=0.33, GC dose reduction in mg/day 5 (0-8) vs 4 (0-7.5), p=0.77, respectively). At baseline, 86.6% of patients with low BMI were categorized in at least moderate activity according to the DAS28, whereas after 6 months, 53.3% were in remission and 10% only had low disease activity. In patients with high BMI, a similar effect was observed. Patients who did not comply with the recommended infusion cycle regimen benefited from TCZ treatment similarly well as patients who did comply.

Conclusions Treatment of RA with TCZ over a period of 6 months leads to a significant reduction of the DAS28, TJC and SJC number and a reduced need for GC use. These beneficial effects were observed irrespective of patients' BMI. Furthermore, not complying with the recommended infusion cycle regimen did not result in worse outcomes.

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